Making bimetallic billet



Jan. 15, 1957 J. BERKELEY MAKING BIMETALLIC BILLET 16 Sheeis-Sheet 1 Filed March 11, 1954 INVENTOR L. J. BERKELEY MAKING BIMETALLIC BILLET Jan. 15, 1957 16 Sheets-Sheet 2 Filed March 11, 1954 L. J. BERKELEY MAKING BIMETALLIC BILLET Jan. 15, 1957 16 Sheets-Sheet 3 Filed March 11, 1 54 Jan. 15, 1957 J. BERKELEY 2,777,936

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MAKING BIMETALLIC BILLET Filed March 11, 1954 16 Sheets-Sheet 14 mil/1x11111111 INVENTOR [a are/me .1 FerIe/y 1957 J. BERKELEY 2,777,936

MAKING BIMEJTALLIC BILLET Filed March 11, 1954 l6 Sheets-Sheet 15 INVENTOR euro/me JZerJe/y 2 am/r Jan. 15, 1957 E E 2,777,936

MAKING BIMETALLIC BILLET Filed March 11, 1954 16 Sheets-Sheet 16 INVENTOR Z curenee J. Ber {Q19 %w/ 2:4 4.; 7

MAKING BIMETALLIC BILLET Laurence J. Berkeley, Danville, Ill., assignor to Superior Steel Corporation, Pittsburgh, Pa., a corporation of Virginia Application March 11, 1954, Serial No. 415,594

2 Claims. (Cl. 219--73) This invention relates to the making of bimetallic billets. It relates particularly to a method of and apparatus for assembling and maintaining in assembly in proper cooperative relationship the components of a bimetallic billet.

I form a bimetallic billet by applying to a backing component which may, for example, be of carbon steel, a facing component or facing components which may, for example, be of gilding metal, copper, aluminum, stainless steel or other metal by applying the facing component or components to the backing component and holding the components in assembly by fastening means connected with the backing component at the edge faces thereof and extending into holding relationship with the facing component or components.

The fastening means at each edge face of the backing component may comprise a generally planar body portion lying against the backing component and means extending transversely of the general plane of the body portion engaging and holding in place the facing component or components. For example when a bimetallic billet is to be made comprising a backing component with facing components at opposite faces of the backing component the fastening means may comprise generally channel-shaped elements having their bodies or webs lying against the edge faces of the backing com ponent and connected with the backing component, for example by welding, and having their holding portions or flanges extending substantially at right angles to the Webs and overlying the edges of the facing components to clamp the facing components to the backing component. The channels may when applied to the backing component have their flanges extending at obtuse angles to the webs of the channels and the flanges may thereafter be pressed, for example by rolls, into clamping engagement with the facing components. The facing components may be narrower than the backing component to allow for differential lateral expansion. The pressure with which the flanges of the channels are pressed into clamping engagement with the facing components is controlled to allow for differential lateral expansion.

The fastening means may be applied to the backing component by continuous welding longitudinally of the assembly. The assembled backing component and fastening means (preferably with the facing component or components also assembled therewith) may be relatively moved in the direction of the length of the assembly in respect to welding apparatus; I prefer to mount the Welding apparatus at a welding station and advance the work continuously through the welding station, although the work might be maintained in fixed position and a welder moved therealong. Each fastening element may be welded to the backing component by one or a plurality of welds; I prefer to weld fastening channels to the backing component by two continuous longitudinal Welds at opposite sides of the longitudinal axis of each channel. I prefer to employ arc welding which fuses lnited States Patent a zone of the metal of the web of the fastening element completely through the web and a zone of the metal of the backing element contiguous to the first mentioned zone so that when the metal cools the fastening element is welded to the backing component by a substantially unitary metal connection. Supplemental weld metal may be added during the welding.

While the orientation of the work may be varied, I prefer to arrange the backing component in a horizontal plane with the facing component or components disposed against its top and/or bottom face or faces and to advance the assembly horizontally lengthwise through the welding station, the fastening means being applied to the generally vertical edge faces of the backing component.

For purposes of explanation and illustration I shall. describe the making of a bimetallic billet comprising a relatively thick relatively wide elongated carbon steel backing component and two relatively thin relatively narrow elongated facing components of gilding metal, one of the facing components being somewhat thicker than the other but both being quite thin in relation to the backing component. I first dispose the thicker facing component in position and place the backing component atop it and then place the thinner facing component atop the backing component. The thus assembled components are advanced longitudinally, as, for example, on a roller table, to a station at which means are brought into engagement with the side edges of the components to insure that each of the three components is properly oriented in the line of advance of the assembly through the welding station and with each of the facing components laterally centered with respect to the backing component. Fastening channels are then applied to the side edge faces of the backing component, the flanges of the channels being initially disposed at obtuse angles to the web thereof so that the channels are slightly open in comparison with channels having their flanges at right angles to their webs. This is to facilitate application of the channels without interference by the facing components. Since one of the facing components is thicker than the other the channels must be positioned slightly off-center relatively to the backing component. The channels are set in place by hand and initially temporarily clamped to the backing component by hand clamps extending across the assembly and engaging the outsides of the webs of the respective channels.

The thus assembled components are advanced through the welding station. At the welding station the channels are clamped to the backing component by rolls so that the temporary hand clamps may be removed. In the present preferred embodiment of the apparatus herein disclosed two welds are formed between each channel and the backing component. Since the channels are arranged with their webs substantially vertical the welds extend substantially horizontally through the channels and into the vertical edge faces of the backing component, the welds for each channel being disposed one above the other and each weld being substantially continuous longitudinally of the billet. In the apparatus disclosed the welds are formed by arc welding. Each weld is formed by an electrode which draws an arc from the channel, the current passing through the channel and through the backing component to which another electrode extends to complete the electrical circuit. I prefer to form the weld by submerged arc welding and I apply flux, preferably in powdered form, during forma tion of the weld. The flux is supported by suitable means disposed in contiguity to the outer surfaces of the webs of the channels. I prefer to use generally horizontal endless belts which travel at substantially the same speed as the work, one belt for each weld disposed at a level just below the level of the weld, the belts therefore being disposed at different elevations, the upper belt discharging its flux onto the lower belt. The upper weld is formed ahead of the lower weld so that flux from the upper weld may also be used in forming the lower weld. I provide means for recirculating and continuously supplying flux to the welds. The flux discharged by the upper belt onto the lower belt may be supplemental to additional flux supplied to the lower belt. I continuously supply welding rods constituting the electrodes which draw the arcs.

The flanges of the channelsare rolled down into clamping engagement with the edges of the facing components, preferably after the channels have been welded to the backing component, the pressure applied being controlled so that the flanges tightly clamp the facing components to the backing component yet allow for differential lateral expansion, i. e., for lateral expansion of the facing components relatively to the backing component under the flanges of the channels. Unless such differential lateral expansion is provided for the facing components may bow up in the middle. The completed billet is delivered from the apparatus by suitable means such as a roller table and is ready for heating and hot rolling.

Other details, objects and advantages of the invention will become apparent as the following description of a present preferred embodiment thereof and a present preferred method of practicing the same proceeds.

In the accompanying drawings I have shown a present preferred embodiment of the invention and have illustrated a present preferred method of practicing the same, in which Figure l is a schematic drawing of the apparatus illustrating somewhat diagrammatically the welding unit, the entrance and exit conveyors and the crimping rolls and stand;

Figure 2 is a cross-sectional view of a finished billet showing the channels welded to the backing component and the flanges of the channels crimped onto the two facing components;

Figure 3A is a simplified partial top plan view of the left half of the welding unit showing the entrance and exit drive rolls on the left half of the welding unit, the associated hydraulic cylinders for opening and closing the entrance drive rolls, the flux belt driving motor and means for transversely adjusting the position of the flux belt assembly;

Figure 3B is a partial top plan view of the right half of the welding unit showing the elements corresponding to those shown in Figure 3A and -showing additionally the Welding heads, the electrodes, the flux belt drive shafts and the flux belt assembly;

Figure 4A is a partial end elevation of the welding unit showing the left-hand side as viewed from the entrance end;

Figure 4B is a partial end elevation of the welding unit showing the right-hand side as viewed from the entrance end;

Figure 5 is a side elevation of the welding unit;

Figure 6 is a sectional view of the welding unit sighting transverse to the center axis;

Figure 7 is a side elevation of the entrance conveyor;

Figure 8 is a plan view of the entrance conveyor;

Figure 9 is a plan view of the exit conveyor and crimping roll stand;

Figure 10 is a side elevation of the exit conveyor and crimping roll stand;

Figure 11 is an end view of the crimping roll stand and driving means;

Figure 12 is a side elevation of the motor and variable speed drive means for the drive rolls for advancing the assembly of billet components through the welding unit;

Figure 13 is an end elevation of the motor and variable speed drive means shown in Figure 12;

Figure 14 is an elevational view of the right-hand upper and lower flux belt assemblies taken from the center line of the mill and in a direction parallel to the planes of the longitudinal reaches of the belts;

Figure 15 is a fragmentary plan view of the righthand upper and lower flux belt assemblies in a direction perpendicular to the planes of the longitudinal. reaches of the belts;

Figure 16 is a fragmentary transverse sectional view taken along line XVIXVI of Figure 14;

Figure 17 is a fragmentary elevational view showing one of the welding heads and flux belt drive motors;

Figure 18 is an enlarged transverse sectional view of the entrance conveyor taken on the line XVIII-XVII of Figure 7 showing one of the centering units;

Figure 19 is a fragmentary plan view showing one of the centering units;

Figure 20 is an enlarged fragmentary transverse sectional view showing one of the entrance drive rolls of the welding unit;

Figure 21 is a fragmentary transverse sectional view showing one of the exit drive rolls of the welding unit;

Figure 22 is an enlarged fragmentary transverse sectional view of the entrance conveyor taken on line XXIIXXII of Figure 7 showing an assembly of billet components in place thereon;

Figure 23 is an enlarged transverse sectional view of the entrance conveyor taken on line XXlll-XXl-II of Figure 7;

Figure 24 is an enlarged transverse sectional view of the entrance conveyor taken on line XXIV-XXIV of Figure 7;

Figure 25 is an enlarged transverse sectional view of the entrance conveyor taken on line XXV-XXV of Figure 7;

Figure 26 is a plan view of the gear train housing showing diagrammatically the arrangement of the gears for driving the entrance and exit drive rolls of the welding unit;

Figure 27 is an enlarged transverse sectional view taken along line XXVll-XXVII of Figure 26;

Figure 28 is an enlarged longitudinal sectional view taken along line XXV ll l-XXV ill of Figure 26; and

Figure 29 is a wiring diagram for the welding uni-t.

Referring now more particularly to the drawings, the apparatus, shown schematically in Figure 1, comprises generally an entrance conveyor ll, a welding unit 2, an exit conveyor 3 and crimping means 4.

Figures 2.2, 23, 24 and 25 are cross-sectional views showing details of the entrance conveyor 1. Rotatably mounted in bearings '1 the frame the conve or is a transverse shaft 22d (F 7 and 22) having rollers 11 fixed thereon. The shaft is not driven but the rollers and shaft are free to turn when the assembly of billet components is advanced along the entrance conveyor by turning of the driven rollers 5 and Drums are mounted on the rollers 11 and stened thereto by bolts lla as shown in Figure 2 2. example, Figure 8) that drun g on the rollers 11 carried by the shaft but also on certain of the rollers $3. The drums are for positioning fastening channels as will presently be described. The shaft 222i? has fixed thereto 'eeves inwardly of t' e bearings 221, and W2.

surround the shat bear against the inner ends C1. the sleeves 211352, the washers being held apart by a compression coil spring Fudless chains 225 pass over the sleeve 2322 and dip into a pool of oil 22s contained in a reservoir 226:: formed in the bottom of the entrance conveyor. Turning of the shaft and the sleeves 24.51 causes the endless chains 225 to turn about the shaft and carry oil upwardly from the pool of oil The oil is transferred from the chains to the sleeves and thence to the bearings 221.

Fixed to the shaft that of the motor 10 is a V-belt pulley 227 (Figures 7 and 25) driving V-belts 228. The

V-belts 228 extend about and drive a pulley 229 fixed to a shaft 230 mounted for rotation in bearings 234 in the frame of the conveyor. Also fixed to the shaft 230' is a gear 231. The gear 231 meshes with a gear 232 (Figure 7) fixed to a shaft 233 which is mounted for rotation in the frame. Through similar mechanism the motor 7 drives a shaft 233 mounted for rotation in the frame in bearings 235. A gear 231a similar to the gear 231 is fixed to the shaft 2341 and meshes with a gear 232 fixed to the shaft 233 (Figures 7 and 24). The gear 232 dips into the pool of oil 226 for lubricating the gear train of which the gear 232 is a member. Some of the oil also passes to and lubricates the bearings 235. The gear train and bearings associated with the drive from the motor 10 are similarly lubricated.

Keyed to the shaft 233 is a sprocket 236 which drives an endless sprocket chain 237 which meshes with a sprocket 238 (Figures 7 and 23). The sprocket 238 is fixed to a shaft 239 which is journaled for rotation in bearings 24!). The sprocket chain 237 carries oil from the pool of oil 226 to lubricate the associated working parts. Also fixed to shaft 239 is a sprocket 241 which drives an endless sprocket chain 242. meshes with a sprocket 243 fixed to a shaft 244 journaled for rotation in bearings 245.

Also fixed to the shaft 244 is a sprocket 246. Sprocket 246 drives an endless sprocket chain 247 which meshes with the sprocket 248 fixed to a shaft 249 journaled in the frame. In this way the shaft 249 is driven. Each of the shafts 244 and 249 has fixed thereto opposed rollers 5. When the shafts are driven the rollers turn and advance work disposed upon the rollers.

Also fixed to shaft 249 is a sprocket 250 which drives an endless chain 251 which meshes with a sprocket 251' fixed to a shaft 252. By a similar arrangement including an endless sprocket chain 254 a shaft 253 also journaled in the frame is driven by the shaft 252. Rollers 5 are also fixed to the shafts 252 and 253.

Mounted adjacent the entrance conveyor for cooperation therewith are two centering units 13 (Figures 18 and 19). The distance longitudinally of the conveyor between the two centering units 13 is somewhat less than the len th of assemblies of billet components to be operated on by the apparatus. Each centering unit comprises opposed double-acting hydraulic cylinders 14 in which rams 15 operate. End plates 16 on the rams carry upper index blocks 17 and lower index blocks 18, which blocks are both removable and adjustable. When the upper facing component 19, the backing component 20, and the lower facing component 21 of an assembly to be formed into a bimetallic billet (Figure 2) are disposed on the conveyor in transverse alignment with the two rams the operator manipulates a valve (not shown) and hydraulic pressure is applied at the outer ends of the cylinders 14 forcing the rams 15 toward the center line of the entrance conveyor 1. The upper index blocks 17 engage the upper facing component 19, the bodies of the lower index blocks 15 engage the backing component and projections 18a of the lower index blocks 18 engage the lower facing component 21. The blocks are replaceable and adjustable on the end plates 16 to properly cooperate with components of various sizes making up assemblies operated on by the apparatus. The two rams 15 of each centering unit 13 are interconnected through a linkage 22 shown in Figure 18 which maintains them equidistant from the center line of the entrance conveyor at all times. Thus when pressure is applied at the outer ends of the double-acting hydraulic cylinders 14 the index blocks 17 and 18 engage the upper and lower facing components and the backing component and center them with respect to each other and with respect to the center line of the entrance conveyor. After the components are centered by the two centering units the rams are retracted to free the assembly for further processing as will be explained.

The chain 242 The welding unit is generally shown in Figures 3A, 3B, 4A, 4B, 5 and 6. Double-acting hydraulic cylinders 23, 24, 25 and 26 are mounted in pairs on the frame 27 of the welding unit, there being two cylinders 23 one above the other at one side of the welding unit opposed by two cylinders 24 one above the other at the opposite side and there being two cylinders 25 one above the other at the first mentioned side of the welding unit in alignment longitudinally of the apparatus with the respective cylinders 23 and opposed by two cylinders 26 one above the other at the second mentioned side of the welding unit in alignment longitudinally of the apparatus with the respective cylinders 24. Rams 28 operate in the cylinders. Mounted on the ends of the rams in the respective pairs of cylinders 23, 24, 25 and 26 are supports 29, 30, 31 and 32; that is, each support is carried by two vertically superimposed rams. Each of the supports 29, 30, 31 and 32 has upper and lower projecting portions 33 (Figure 20) Each portion 33 comprises a roller bearing 34. A shaft 35 is journaled in each vertically aligned pair of roller bearings 34. Cylindrical sections 36 and spacers 37 are mounted on each shaft 35 between members 33. The cylindrical sections are fastened in place on the shafts 35 by set screws 38. The cylindrical sections are grooved on the outside and have milled edges on the raised portions adapted to engage the assemblies as they move through the welding unit. Each of the entrance drive rolls 39, 40; 41 and 42 (Figures 3A and 313) comprises the assembly of a shaft 35 with cylindrical sections 36 and spacers 37 thereon. Projecting from the upper por tion 33 associated with entrance drive roll 39 is a rack 43 meshing with a pinion 4 rotatably mounted in a bracket 45 carried by the frame 27 (Figures 3A and 3B and 4A and 4B). A rack 46 similarly projects from the upper portion 33 associated with entrance drive roll 44) and meshes with pinion 44. Because of this interconnection the entrance drive rolls 39 and 43 must move inwardly and outwardly together and be at all times equidistant from the center line of the welding unit. The other entrance drive rolls 41 and 42 are similarly interconnected by racks 47 and 48 and pinion 49 and act cooperatively as do the rolls 39 and 49.

A slot 50 is cut in the top of each shaft 35 (Figure 20) to accommodate the cross pin of a universal joint. The entrance drive roll 39 is driven by a universal joint 51 (Figure 4B) which fits over the end of shaft 35. The other end of the universal joint is connected to a member 52 which ends in a splined section 53 fitting inside and engaging tubular member 54 so as to be held against rotation but free to move longitudinally relatively thereto. Tubular member 54 is in turn driven through a universal joint 55 by a shaft projecting downwardly from a train of gears (presently to be described) in a gear box 56. Thus the drive roll 39 may be driven regardless of the position of rams 28. The universal joints will transmit power when the members 52 and 54 are at any angle relatively to the gear box and drive roll. The extensible shaft comprising members 52 and 54 will adjust itself to any required length. The remaining entrance drive rolls 4t), 41 and 42 are similarly driven from the gear box 56.

Attached to the shaft 56a of an electric motor 57 (Figures 12 and 13) is a split pulley comprising opposed cooperating halves or sections 58 and 59. Pulley section 58 is fixed to the motor shaft. Pulley section 59 is splined to the motor shaft so as to be held against rotation but free to move longitudinally relatively thereto. Pulley section 59 is resiliently urged toward pulley section 58 by a spring attached to the outer end of the motor shaft and located within the hollow cover 60. The peripheral faces of the two pulley sections 58 and 59 are tapered and converge toward the motor shaft. A belt 61 is disposed about the split pulley. As pulley section 59 moves away from pulley section 58 the effective diameter of the split pulley is reduced and belt 61 will be allowed to more closely approach the motor shaft. Belt 61 is also disposed about a conventional pulley 62 fastened to a shaft 63. The motor 57 is mounted on a bracket 64 carried by a generally upstanding frame 65 for generally vertical sliding movement relatively thereto. The frame 65 is carried by the welding unit frame 2'7. Rotatably mounted in frame 65 is a generally vertical threaded shaft 66 which is rotated by turning hand wheel s7 which is fixed to the shaft at the upper end thereof. The threaded shaft as passes through portions 66a of the bracket as which are drilled and tapped to engage with the threads of shaft 66. By rotating shaft 65 the bracket 64- and hence the motor 57 carried thereby may be raised or lowered with respect to frame 65. As the motor moves upwardly the tension on belt 61 increases, causing the pulley section 59 to move outwardly against the action of the spring in the hollow cover all, thereby reducing the effective diameter of the pulley. This in turn reduces the speed at which the driven shaft 63 is rotated. Conversely, as the motor moves downwardly relatively to the frame 65 the tension on belt 61 decreases, allowing the spring to move the pulley section toward the pulley section 58 and increases the effective diameter of the pulley. This in turn increases the speed at which the driven shaft 63 is rotated.

Also fixed to shaft as is a sprocket 68 with which an endless sprocket chain 69 meshes. The endless sprocket chain 69 also meshes with another sprocket 7b fixed to the shaft 7% of an oil pump 71. The oil pump rccirculates oil from the sump of gear box 56 over the gears therein.

Shaft as (Figures 26 and 27) has a portion thereof formed as a worm 72 which meshes with a worm wheel 73 fixed to a shaft 73a. The shaft 73a in turn drives the gears 74, '75, 7s, '77, 78 and '79 through the gear train in the gear box 56. The direction of turning of the respective gears is indicated by arrows in Figure 26. Gear 74 is fixed to the previously mentioned shaft 80 which projects from the lower side of the gear box (Figure 4B) and drives entrance drive roll 35 through the universal joints 51 and 55 and connecting members 52 and 54. In like manner gears 75, 7n and 77 drive entrance drive rolls ll and 42, respectively. Thus the motor 57 drives the four entrance drive rolls simultaneously. The gear train is designed so that the entrance drive rolls are all driven at the same speed and in respective directions to advance an assembly of billet components through the welding unit from left to right viewing Figure 1 when the rolls are in driving engagement with the assembly as will be described.

Generally opposed double-acting hydraulic cylinders ill and are mounted on frame 27 (Figures 3A and 3B). Rams 553 project from the inner ends of the respective cylinders. Each ram 83 carries a support .54 which in turn carries roller bearings 35 (Figure 21) in which is journaled a shaft 87. Fixed to the lower end of each shaft 87 is an exit drive roll; the opposed exit drive rolls are designated as and 9%, respectively (Figures 3A, 3B and 2 The exit drive rolls are milled as indicated at 88a in Figure 21 to engage the assemblies (then completed billets) being driven out of the welding unit. The exit drive rolls 89 and 95 are driven respectively by gears 78 and 7& (Figure 26) through universal joints and extensible shafts similarly to the entrance drive rolls. Gears '78 and 79 are driven at the same speed as gears 74, 75, 7d and 77 by using appropriate gearing between them. The rams 33 carry opposed racks Ellie and 96b meshing with a pinion 9% as shown in Figures 3A and 3B whereby to insure that the exit drive rolls $9 and 99 are at all times equidistant from the center line of the welder.

The frame 27 carries at each side a support 91 (Figures 4A and 4B) carrying for guided longitudinal movement transversely of the welder a rack Meshing with each rack 93 is a pinion 96 fixed to a shaft journalled in the corresponding support 91 and which shaft is turned by a hand wheel W (Figures 3A and 3B) through gearing in a gear case 9b. Turning of either hand wheel 99 will independently move the corresponding rack 93 toward or away from the center line of the welder.

Connected with each rack 93 is a support l l'll upon which is mounted an electric motor Each motor lill drives through reduction gearing in a gear case 102 a shaft 1193 which through a coupling drives a shaft Each shaft 105 is connected through a universal joint 1% with a shaft 107 which in turn is connected through a universal joint MP9 with a shaft 1st for driving the corresponding upper flux belt lilti (Figures 6, 14, 15 and i6). Fixed to each shaft M5 is a sprocket limb with which meshes a sprocket chain 111 which also meshes with a sprocket lllla fixed to a shaft 1W jourualled in the corresponding support hill. Each shaft lib drives the corresponding lower flux belt EH12 (Figures 6, l4, l5 and i6) through universal joint 1M, shaft 113, universal joint US and shaft By the mechanism thus provided the flux belts may be adjusted in position toward and away from the center line of the welder while being continuously connected with their driving means.

At each side of the welder the upper flux belt assembly is carried by a support 126 (Figures l4, l5 and 16) which in turn is carried by a vertical rack (Figures 4A and 45) mounted for vertical movement on the corresponding horizontal rack 93. Each rack. 125 is moved up or down by a pinion 122 (Figure 5) meshing therewith, the pinion being fixed to a shaft $.20 journalled on the corresponding rack 93. The outer end of each shaft 120 is squared as shown at 121 to receive a wrench for turning the shaft. Turning of either shaft 12% thus changes the elevation of the upper flux belt assembly at the corresponding side of the welder. The change in elevation of an upper flux belt assembly does not interfere with driving of the corresponding upper flux belt 1% through the mechanism above described since the universal joints compensate for changes in elevation of the belt.

Similarly the lower flux belt assembly at each side of the welder is carried by a bracket 134 (Figures 14, 15 and 16) which in turn is carried by a vertical rack 132 (Figure 5) mounted for vertical movement on the corresponding horizontal rack 93 similarly to the vertical racks 125. Meshing with each vertical rack 132 is a pinion 13ft fixed to a. horizontal shaft 127 journalled for rotation in the corresponding horizontal rack 93. The end of each shaft 127 is squared as shown at 127a to receive a wrench for turning the shaft. Thus the lower flux belt assemblies are mounted and vertically adjustable analogously to the corresponding upper flux belt assemblies.

Figures 14, 15 and 16 show the upper and lower flux belt assemblies at the right hand side of the welding unit viewing Figures 4A and 4B. Fixedly mounted on the bracket 13 is a bearing bracket 7.35 in which is journalled for rotation the shaft 1% carrying a pulley 137 about which the lower flux belt M2 is trained. Four bolts 138 are threaded into the bearing bracket 135. Surrounding each bolt is a bushing i139. Atop the bushings 139 and held down by the heads f the bolts is a plate 143. Disposed about each bushing 139 are upper and lower grooved rollers and Mt with a spacer 142 therebetween a shown in Figures 14 and to. The total axial dimension of the rollers Md and Al and the spacer 142 disposed about each bushing 13? is slightly less than the axial dimension of the bushing so that the rollers are free to turn about the bushing.

A second bearing bracket i i-i ha journalled therein a shaft 145 carrying a pulley 1 56 about which the lower flux belt 112 is also trained as shown in Figure 14. The bearing bracket 1 .44 has a portion passing between the opposed lower grooved rollers 141 and entering the 

